1. Field of the Invention
This invention relates to a coated abrasive product having a pressure-sensitive adhesive layer coatable from water.
2. Discussion of the Art
Many coated abrasive products, especially coated abrasive sheets and discs, are mounted on a support pad, sometimes called a back-up pad, during use. The purpose of the support pad is to provide the coated abrasive with the necessary foundation required for a particular abrading application. For example, if the coated abrasive article is to be employed at high pressure, e.g., for high stock removal applications, the support pad will typically be durable, heat resistant, and rigid. If the coated abrasive article is to be employed for finishing contoured surfaces, the support pad will typically be soft and conformable.
One means for securing the coated abrasive article to the support pad calls for a pressure-sensitive adhesive. Typically, the surface of the coated abrasive article not containing the abrasive grains will bear a layer of pressure-sensitive adhesive. The pressure-sensitive adhesive of this layer must have sufficient adhesion to hold the coated abrasive article on the support pad for the intended abrading application. In some cases, the coated abrasive/support pad assembly rotates as many as 15,000 rpm. If the pressure-sensitive adhesive does not have sufficient adhesion, the coated abrasive article can fly off the support pad at high rotation speeds, thereby resulting in excessive downtime.
A wide variety of pressure-sensitive adhesives have been utilized with coated abrasive products in the past. U.S. Pat. No. 2,286,208 discloses coated abrasive products having several different types of solvent-based pressure-sensitive adhesives. These pressure-sensitive adhesives include ethyl cellulose adhesives, alkyd resins, rubber-based adhesives, and rosin-based adhesives.
U.S. Pat. No. 2,544,940 discloses a polishing pad for use with loose abrasive grain. The polishing pad is adhered to a support pad by a natural, synthetic, or chlorinated rubber.
U.S. Pat. No. 2,888,785 discloses a coated abrasive that is adhered to a support pad by a rubber-based pressure-sensitive adhesive.
U.S. Pat. No. 3,849,949 discloses a convolutely wound roll of coated abrasives, each of which contains a pressure-sensitive adhesive coating on the non-abrasive side. In one embodiment, the pressure-sensitive adhesive is a water-based acrylate adhesive.
U.S. Pat. No. 3,875,703 discloses a coated abrasive disc that is adhered to a support pad by a rubber-based latex adhesive.
For many years, pressure-sensitive adhesives have been coated from organic solvent solutions onto the non-abrasive side of the coated abrasive article with excellent results. However, because recent governmental regulations require reductions in solvent emissions, the coated abrasive industry should eliminate all organic solvents from their coating operations. Accordingly, it would be desirable to replace pressure-sensitive adhesives coated from organic solvents with pressure-sensitive adhesives coated from water. In some applications, especially those involving high rotation speeds and high grinding pressures, currently available pressure-sensitive adhesives coated from water do not exhibit sufficient adhesion to consistently prevent abrasive discs from flying off support pads. Accordingly, for some products, the coated abrasive industry is forced to rely on pressure-sensitive adhesives coated from organic solvents in order to obtain the required adhesive properties.